1. Field of the Invention
The present invention relates to a chemical-agent extrusion assisting-tool adapted for use in extruding a highly viscous chemical agent from a syringe barrel or a similar container through, for example, an injection needle or a catheter, as well as to a method for extruding a chemical agent using the chemical-agent extrusion assisting-tool. The chemical-agent extrusion assisting-tool of the present invention facilitates extrusion of a highly viscous chemical agent such as bone cement through, for example, an injection needle connected to a syringe barrel. The chemical agent extrusion assisting-tool of the present invention is thus useful in filling bone cement, such as calcium-phosphate-based cement, into a defective portion of an organic bone caused by bone fracture or osteoporosis or in applying the same for serving as an adhesive for bonding an artificial bone, formed from metal or ceramic, to an organic bone. The invention also relates to a method for extruding a chemical agent using the chemical-agent extrusion assisting-tool, a kneader for use in preparing the chemical agent and to form the container from which the chemical agent is to be extruded using the chemical-agent extrusion assisting-tool. Further, the invention relates to a method for preparing and extruding a chemical-agent using the kneader and the chemical agent extrusion assisting-tool.
2. Description of the Related Art
A gun-type ejector for aqueous paste dental materials (Japanese Patent Application Laid-Open (kokai) No. 7-255748 and PCT International Application Laid-Open No. WO95/00078) is known as an instrument for extruding through, for example, an injection needle or a catheter, a chemical agent which is so viscous that the user encounters difficulty in extruding by pressing with his/her fingers. A gun-type ejector has also been developed for resin-based bone cement such as polymethyl methacrylate (PCT International Application Laid-Open No. WO94/16951). Further, an ejector has been proposed combined with a pressurizing device such as a compressor (Japanese Patent Application Laid-Open (kokai) No. 5-317333) for calcium-phosphate-based cement, which is a highly viscous sludge-like kneaded substance and which requires a particularly high pressure for extrusion thereof.
However, these ejectors, particularly the ejector combined with a compressor, are of complicated structure and large size and are thus not readily usable. Since ejectors for extruding bone cement in the course of a surgical operation must be sterilized, they are preferably disposable. The ejectors described in the above publications are disadvantageous in terms of cost and size. Further, a gun-type ejector conventionally used for extruding dental materials and resin-based bone cement has an outlet of relatively large diameter and is thus not suited for fine-extrusion applications, such as local filling or application of chemical agent.
It is therefore an object of the present invention to solve the above-mentioned problems of conventional ejectors, and to provide a chemical-agent extrusion assisting-tool enabling extrusion of a highly viscous chemical agent such as calcium-phosphate-based cement through an outlet of small diameter such as an injection needle and capable of being of a disposable type, as well as to provide a method for completely extruding a chemical agent, by use of the assisting tool, from a syringe barrel or a similar container through, for example, an injection needle or catheter connected thereto.
A chemical-agent extrusion assisting-tool in a first aspect of the invention comprises: a tool body in the form of a cylindrical body having a space formed therein for accommodating a tubular container for containing a chemical agent and which has an outlet formed at its bottom end, the cylindrical body having an annular cylindrical space formed therein so as to open at an upper end surface thereof; a pusher comprising a handle portion for pressing a piston to be inserted into the tubular container, and a tubular body disposed on a side of the handle portion which presses the piston, wherein a circumferential surface of the tubular body and a circumferential surface of the cylindrical body which defines the annular cylindrical space are screw-threadedly engaged.
A second aspect of the invention provides a method for extruding a chemical agent using the chemical-agent extrusion assisting-tool defined above, comprising: rotating the handle portion so as to screw-engage the tubular body and the circumferential surface of the cylindrical body which defines the annular cylindrical space so as to press the piston into the tubular container, thereby extruding the chemical agent from the tubular container.
The tubular container for containing a chemical agent can be a syringe barrel generally used for filling or applying a chemical agent such as calcium-phosphate-based cement to a required location. Appropriate determination of the diameter and length of the columnar space of the tool body enables use of a container having a certain structure and dimensions, other than general syringe barrels.
The term xe2x80x9ccontainxe2x80x9d as used herein includes the following two cases: a previously prepared chemical agent is filled into the tubular container; and powder and a kneading liquid, for example, calcium phosphate powder and a kneading liquid for preparation of calcium-phosphate-based cement, are mixed and kneaded within the tubular container.
Thus, a third aspect of the invention provides a kneader for use as a tubular container with the chemical-agent extrusion assisting-tool according to the first aspect, the kneader comprising: a cylinder to be accommodated in said space formed in the tool body and having a cylindrical portion and a nozzle portion formed at one end of the cylindrical portion; a plug disposed slidably within the cylindrical portion; a piston which includes a shaft portion extending through the plug for rotation relative thereto so as to cause movement of the piston axially of the cylinder, a kneading portion located at an end of the shaft between the plug and the nozzle portion, and a handle portion location at the other end of the shaft for engagement by the pusher; a stopper for releasably holding the plug at the other end of the cylindrical portion; and a cover removably attachable to the nozzle portion.
A fourth aspect of the invention provides a method for preparing and extruding a chemical agent using the kneader according to the third aspect and the chemical-agent extrusion assisting-tool according to the first aspect, comprising: introducing constituents to be mixed and kneaded to form the chemical agent into the cylinder of the kneader; turning the handle portion of the piston with the plug fixed by means of the stopper and the cover attached to the nozzle portion so as to rotate and axially move to the kneading portion within the cylindrical portion, and thereby to knead the constituents and form the chemical agent; fitting the cylinder into the space formed in the tool body with the kneading portion returned to said other end of the cylindrical portion adjacent to the plug and removing the cover from the nozzle portion; releasing the stopper; and rotating the handle portion of the pusher so as to screw-engage the circumferential surface of the tubular body and the circumferential surface of the cylindrical body which defines the annular cylindrical space so as to cause the pusher to press the piston and the released plug into the tubular container thereby extruding the previously kneaded chemical agent from the kneader.
The chemical-agent extrusion assisting-tool is useful for extruding those chemicals which the user encounters difficulty in extruding through, for example, an injection needle by pressing with his/her fingers. Examples of such chemicals include a bone cement and more particularly a calcium-phosphate-based cement. Calcium-phosphate-based cement is prepared from calcium phosphate powder and a kneading liquid. After setting, calcium phosphate powder is converted to hydroxyapatite. The thus-formed set substance has sufficient strength to serve as a prosthetic material for bone and exhibits excellent bio-compatibility and bio-activity. Accordingly, calcium-phosphate-based cement is useful for formation of, for example, artificial bone, artificial joints, and artificial tooth roots having excellent strength and bio-activity.
Examples of calcium phosphate powder include tetracalcium phosphate, calcium hydrogen phosphate, xcex1-tricalcium phosphate, and xcex2-tricalcium phosphate. These powders may be used singly or in combination. Calcium phosphate powder may be mixed with X-ray contrast medium, such as barium sulfate or bismuth subcarbonate. In order to shorten setting time, hydroxyapatite or fluoride may be added as seed crystals.
Examples of the kneading liquid include water, such as pure water, and an aqueous solution which contains an appropriate amount of polysaccharide, such as dextran sulfate, an organic acid, or an inorganic acid.
The foregoing and other objects, features, aspects and advantages of the present invention will become more apparent from the following detailed description of the present invention when taken in conjunction with the accompanying drawings.